Tesco is set to install hi-tech screens that scan customers' faces in petrol stations so that advertisements can be better targeted at them.

The retailer will introduce the OptimEyes screen, developed by Lord Sugar's Amscreen, to all 450 of its UK petrol stations, in a five-year deal, according to The Grocer magazine.

The screen, positioned at the till, scans the faces of customers to determine age and gender, and then runs tailored advertisements.

The technology also adjusts adverts depending on the time and date, as well as monitoring customer purchases, The Grocer said.

The screens are predicted to reach a weekly audience of more than five million adults.

Simon Sugar, chief executive of Amscreen, told the industry magazine: "Yes it's like something out of Minority Report, but this could change the face of British retail and our plans are to expand the screens into as many supermarkets as possible."

Nick Pickles of Big Brother Watch said: "Scanning customers as they walk through the store without customers ever giving permission for them to be scanned in that way ... There's a huge consent issue there."

He said facial recognition technology is getting more advanced all the time, adding that you could be queuing to pay for groceries and a CCTV camera could be "literally scanning who you are".

Mr Pickles added that companies and stores using this system must tell their customers.

"If people were told that every time they walked into a supermarket, or a doctor's surgery or a law firm, that the CCTV camera in the corner is trying to find out who they are, I think that will have a huge impact on what buildings people go into," he said.

Mr Pickles said the only way the systems can be ethically deployed is if consumers opt in to have their image stored and their behaviour tracked, rather than there being no choice in the matter.

Tesco point out the technology is not new, and is used by other retailers.

The system makes a 'guess' at whether someone is male or female, and which of three age categories they fall into.

The retailer stresses the screens do not use eyeball scanners, facial recognition, or identify individual customers in any way.